1. Field of the Invention
The present invention relates to a cleaning unit for removing toner and paper dusts that remain on the surface of the photoconductive drum and an image forming device having the cleaning unit.
2. Description of the Related Art
In electrophotography-type image forming devices including copying machines and laser printers, first, an optical image based on image information is exposed by an exposure unit on the surface of a photoconductive drum charged by a charger to form a latent image, and a developing unit feeds toner to convert the latent image into a toner image. Then, the toner image on the peripheral surface of the photoconductive drum is transferred onto a record sheet by a transfer roller and then, heated and pressed to be fixed on the record sheet.
The image forming device includes a cleaning unit for collecting toner (also called waste toner) and paper dusts, which remain on the surface of the photoconductive drum without being transferred to the record sheet, and temporarily storing and transporting the waste toner toward a waste toner collecting container or the like. The cleaning unit includes a linear transport screw for sending the waste toner to the downstream side in a transport direction (for example, Japanese Unexamined Patent Publication No. 2010-210867).
The cleaning unit has a following problem. That is, since the transport screw is disposed above the photoconductive drum at a distance, to transport the waste toner, much waste toner needs to be stored until it reaches the region where the transport screw is disposed. For this reason, the waste toner is stuck due to stored heat, or paper dusts are accumulated, resulting in that the capability of transporting the waste toner and paper dusts is lowered.
To solve the above-mentioned problem, the transport screw may be made close to the photoconductive drum to reduce the distance. However, a support frame for supporting both ends of the transport screw has various limitations in space for attachment of other parts such as a sealing member, stiffness, and the like and therefore the transport screw cannot be made close to the photoconductive drum in some cases.
On the contrary, under the limitations, by extending the outer diameter of the transport screw, waste toner near the photoconductive drum can be transported. With this configuration, however, space occupied by the transport screw increases, which disadvantageously obstructs miniaturization of the cleaning unit.